I'd like to see some detail pictures of your Sierra. Contrary to popular folklore, the serial dates are not build dates. The date associated with the serial number is the date that number was mechanically stamped on the drop out part. There is no record of a frames build date and there was no record of the final build date. In 1976 Schwinn started stamping the final build date on the headbadges and that's as good as it gets for any build dates. The dropouts starting with November stamped serial numbers were normally used building frames for the next years models. There were times when September and October stamped serials were also used on the next years models like the new 1950 Phantom. I'm wondering if your dropout was at the bottom of a parts barrel that kept getting filled with new pieces before yours was possibly used to build a frame a few months later. It's happened before, and with your next year model equipment I'm wondering if any other 1964 parts were used on your Sierra. There were multiple little changes from one year to the next. For example, the 1963, 1964, 1965 and 1966 all had different brake levers.
GT, I think you could be right… my bike might have been stamped on that day, but probably was built-up later on. Ugh, massive screwup on the chain ring… I do have Huret. I have had my 66 varsity on my mind, which has the Sprint chain rings.
Nevertheless, I still have a mix of mostly 63 parts and some 64 parts on my Sierra… here’s the full list:
Huret FD w/Huret FD post clamp (old style Huret font)
Schwinn Sprint branded RD
Huret 40/47/52 Chain rings
Huret down tube shifters
AVA stem w/Alloy drop handlebars
Weinmann Vainqueur 999 (embossed - not the sticker type) CP brakes
Weinmann “Patent” red-dot brake levers
Schwinn S-6 steel rims w/Normandy “bullet hole” hubs
Atom QR Skewers
Atom Freewheel (14-15-18-22-28) w/Large 9-slot chrome pie plate
“15 Speed” screening is still present (very faint)
Union U40 Pedals w/reflectors (must have been added later, but I think 63 Conti’s had Unions, so who knows)
My fork# is stamped 2098. Thru conversations with Eric Amile earlier this year, both his 63 and 64 Sierra’s are stamped 2098, but the crowns are different. My fork crown match’s his 64. The odd part is the 64 part catalog says the fork was to be #2084.
I’ll post pics at a later date… I’m currently re-lacing the S-6 rims with new stainless spokes. Half the bike is still disassembled after doing some major clean-up. But as you can see, I have some type of hybrid 63/64 Sierra. All the parts match one year or the other.